The use of mobile devices such as mobile phones, smartphones, tablets and similar devices has become common. Many mobile devices include a combination of several wireless subsystems such as, cellular, Wi-Fi, Bluetooth, Near-Field Communication (NFC), Global Positioning System (GPS) and so on.
The inclusion of GPS subsystems in mobile devices has facilitated the development and wide distribution of applications that make use of the fact that such devices are location-aware. Many such applications are in a category referred to as location-based services.
It is known that GPS signals may be inadequate for a mobile device to determine its location in some environments.